Fuse plug



Feb. 7, 1933. H, RUSKIN 1,896,248

FUsLf PLUG Filed Feb. 2, 1931 UNITED STATES PATENT OFFICE HENRY BUSXIN, OF CHICAGO, ILLINOIS v FUSE Application led February My invention relates to fuse plugs and particularly to fuse plugs of the multiple type 1n which a number of fuse links are adapted for selective -connection in a circuit to be controlled so that when one link -blows another link may be connected into the circuit.

An important object of the invention is to provide a fuse plug in which the fuse links are stationarily supported -to be engaged by a contact member for selective inclusion in a circuit to be protected.

A further object of the invention is to provide an arrangement in which all the fuse links except the one connected for service` are fully enclosed so as to be protected against the disruptive discharge and resulting gases when the fuse link in service is blown.

A further object is to provide a spacious chamber within the plug for receivingthe disruption products and the hot gases and permit y rapid expansion thereof and reduction of the pressure, together with a multi-path relief outletfor the gases to the exterior of the plug, whereby the relief of pressure will be gradual and not of an explosive nature. r

A further object is to provide in the plu a terminal member of considerable mass an l of good heat conductive material and presenting an extended surface to the disruption products and gases to thereby Vfunction t0 cool the gases and conduct heat to the exterior of the plug.

A further object is to include in the multiple relief paths the hollow thread of the screw shell surrounding the plug body so that the shell may assist in cooling the gases and prolonging the paths thereof before they reach the exterior of the plug.

Still a. further object of'this invention is to produce a plugcomprising a minimum number of parts which can be economically manufactured and assembled.

The various features of my invention are shown incorporated in the structure disclosed ou the drawing, in which drawing Figure 1 is a plan view of the plug;

Figure 2 is a side elevation of the plug;

Figure 3 is an enlarged section on plane III-III of Figure 1;

Figure 4 is an inner end View of the-plug PLUG 2, 19,31. Serial No. 512,825.

plug body in side elevaelement and insulating Figure 7 'shows the fuse element before application to the plug;

Figure 8-shows one end of the insulating shell before application to the plug; and

Figure 9 is a View similar to Figure 4 showing a modied contact arrangement.

The cylindrical tubular plug body 1G has the head 11 and fitting into the body is the cylindrical switch member 12 having the neck 13 of reduced diameter for extending through the throat 14 in the head 11, the head between the throat 14 and the main bore ofthebody forming a seat for the tapered shoulder 15 of the switch member. The outer end of the switch member neck is slabbed off to leave a flat lug 16 by means of which the switch meniber ma be readily turned in the body member. he plug body and the switch member are of suitable insulating material as, for example, material commercially known as bakelit'e.

The plug body on its outer side below the head 11 has threading 17 for receiving the metallic screw shell 18. A cap or base member 19 seats against the lower end of the body member and the switch member and is held in place by lthe radially extending flange 2O at the end of the screw shell when the shell is applied to the body. This cap or base may be made of the same material as the body and switch member.

A terminal member 21 extends centrally through the cap member 19 and at its outer end has the contact head 22 which abuts against the outer face of the cap member. The contact member is 'of some good electrical and heat-conductive material such as brass or copper and is comparatively of large diameter so as to present considerable mass and an extensive surface.

is cored o'ut to provide a spacious chamber 23 plug- The switch member 12 through the center of which the terminal member21 extends, the member at its upper end having the reduced extension 24 received in the opening 25 in the head ofthe switch member 12.l i

Below the shoulder 15 and above the space 23 the switch member has the radial groove 26 for guiding a contact member 27 shown in Figures 3 and 4 as in the form of ametal block. This Contact member has a guide base 28 having the slot 29 through which the reduced end 24 of the terminal member 21 extends, the terminal member body abutting against the base to hold the contact member in place. A spring 30 interposed between the contact block `and the terminal member `21 tends to shift the terminal block outwardly. As the switch member 12 is turned by means of its lug 16, the contact block 27 will travel along the inner face of'the plug body l0 for selective electrical contact with the fuse links of the fuse elementwhich will now be described.

The fuse element is clearly shown in Figure 7. It is cut from asheet of fuse metal and comprises the body band 31 and a number of links 32 extending at right angles therefrom vand equally spaced apart, six of such links being shown. Each link has a reduced section or neck 33 at which the link will disrupt under abnormal current flow. To receive the link the plug body 10 has the exterior longitudinally extending grooves 34 having the same spacing as the fuse links and on its inner side the plugbody `has corre-- sponding grooves 35, the lower end ofthe plug body having they grooves or notches 36 which join the corresponding outer and inner grooves 34 and 35. As shown in Figures 3 and 6, the fuse element is wrapped around the plug body below thehead 11 and the fuse links are extended through the outer grooves 34u and then bent around the plug end lin lthe slots 36 and then upwardly in the inner grooves 35, the ends of the fuse links terminating within the head 11 of the fuse body.

As shown in Figure 5, the fuse link necks 33 will then be just a short distance above the end of the plug body and above the end cap 19. When the -switch member 12 is inserted through the lower end of the plug'body, it will hold the fuse links in the inner grooves 35 and will Jform an insulating protecting shield between them and the vchamber 23 with the exception of the fuse link which is to be in service. The switch member 12 has the longitudinal slot 37 which will register band 38 and legs 39 extending therefrom spaced apart in accordance with the spacing of the grooves 34. The insulating shell is .fuse links,- the legs terminating at the lower ends of the grooves 34. -After the switch` member 12 has been inserted and thed cap member with the terminal member 21 has been applied, the screwshell is applied to the threading 17 on the plug body and the insulating shell 38 will then be between the screw shell and the outer section of the fuse member. Solder may now be applied. to the overlapping ends of the fuse element and y the adjacent edge of the screw shell, as indicated at 40 (Figure 6), and the fuse element will then be in good electrical connection with the screw shell.

In order to lock the cap member 19 against. rotation relative to t-he plug body, and also to enclose the fuse links where they pass through the slots 36, the cap member is provided with projections or lugs 41 which engage in the slots 36 and against the fuse links,

and then the fuse links will be entirely eny closed and shielded except for the inner end of the fuse link with which the slot 37 and slot 26 are brought into register by the turning of the switch member 12. Upon such registratin the contact block 27 will be in contact with the exposed fuse link and the `circuit to be protected will be closed through the plug by way of the terminal element 21, the contact block 27, the exposed fuse link, and the screw shell 18. When the exposed link is blown under abnormal current flow, the switch member 12 is turned by means of its lug 16 to bring its slot into register with the next fuse link which will then be engaged by the contact block 27. The outer end of the turning lug 16 may be provided with an indicating arrow a: for cooperating with the indicating characters 42 on the face of the head 11 so that the switch member maybe turned to accurately position the contact block 27 for electrical engagement with the -exposed fuse link.

In Figure 9 I show a modified form of contact. Instead of the contact block 27 a Contact spring 43 is 4provided which has the loop 44 for receiving the end of the terminal member 21 to be in electrical engagement therewith and whose other end 45 is in position to engage with the exposed fuse link. The spring is seated in the slot 46 in the head of the switch member so that it must travel with this member when it is turned.

As shown in Figure 4, the lower edge of the plug body 10 has small slots or channels 47 provided therein and preferably extending tangentially or diagonally. After the cap member 19 has been secured in place, these slots will form relief paths from the lill meas-1s chamber 23 to the exterior of the plu body or the space within the screw shell t reads. The chamber 23 extends almost the full diametral width of the switch member 12 so as to provide as large a space as possible within the plug body for the expansion or dissipation of disruption products and gases.'

The terminal element 21 has also considerable width in order to afford a large contact area and also a large mass of metal for cooling` and heat conduction. The fuse `link necks 33 area short distance above the end cap 19 and when the link is disrupted the disruption products or gases will be violently thrown into the space 23, but as this space is large the products may rapidly expand and the pressure relieved. The products find their way through the numerous relief paths 47 and into the thread of the screw shell through which the product must pass before they can reach the exterior of the plug structure. As shown in Figure 3, there 1s sufficient clearance between the screw shell threads and the threading of the plug body and thegases will travel through these clearance spaces andv will find the channels 84 through which `they may escape to the exterior of the screw shell. This multi-path relief of thedisruption product-s gradually relieves the pressure and dissipates the products so that there will` not be any explosive discharge when a use link ruptures, nor will the force of the disruption be concentra-ted on'any one spot to cause burning or breaking.

lVhen the products of disruption encounter the terminal member 21, which is of lar e mass and surface, a great amount of t e generated heat will be withdrawn from the products and conducted to the exterior of the plug structure. Any arc which might forml between the blown fuse linkv and the terminal member 21`will also be spread by the terminal member and thus rapidly exting'uished'1 `All the fuse links with the exception of the onein service will be fully protected from the disruption `products and after one link has blown the switch member is turned to bring another link into service.

Although I have shown a practical embodiment of the various features of my inventibn` l do not desire 4to be limited to the exact kdetails shown and described, as changes and modifications may be made without departing from the scope and principles of the invention as outlined in the appended claims.

I claim as my invention:

j l. In a fuse plug, a. tubular body lpart, a switch member rotatable within sai body part, fuse links supported on the inside of said body part between said part and said switch member, said switch member having a slot for `registering; with a selected fuseV link,

a contact member movable with said switch member for engagement with a selected fuse said body 2. A fuse plug comprising a tubular outer l;

member having a head, a tubular switch member within said outer member and having a. head seated in the head of said outer member and being adapted to be turned in said outer member, fuse vlinks supported between said members, said switch member having a slot for selectively exposing said fuse links when said member is turned, a contact member on said switch member for engaging the selected fuse link, a cap member secured to and closing the inner end of said outer member, a terminal member extending from said cap member into said switch member and having electrical engagement with said contact member, and a terminal member on said outer member electrically connected with said fuse links.

3. A fuse plug comprising a tubular bod a tubular switch member fitting in said bodsy and adapted to be rotated therein, on its inner side having spaced-apart longitudinally extending channels, fuse links in said channels, a contact projecting from said switch member for selective engagement with said fuse links when said switch member is turned, a non-rotatable inner terminal member supported to extend through said switch member into electrical engagement with said Contact member, and an outer terminal member supported on said body and being electrically connected with said fuse links.

4. A fuse plug comprising a tubular body part, a tubular switch part fitting in and rotatable in said body part, said body part at said body i ing from said switch part for selective engagement with said fuse links when said swltch part is turned, an in ner terminal member extending axiallyvthrough said switch i part and in engagement with said contact member, an outer terminal member surrounding said body part and being electrically connected with -said fuse links, said switch part forming a large chamber around substantially the full length of said inner termlnal member, and a multiplicity of restricted outlets from said chamber to the exterior of the plug.

5. A fuse plug comprising a tubular body part, a tubular switch part rotatable within art, sets of outer and inner channels exten ing lon itudinally in the wall of said body part, a se element comprising a band wrapped around said body part and fuse links extending from said band and folded around the end of said body part to engage in the outer and inner channels therebetween said body part and switch part, contact means extending from said switch part for selective engagement with the .fuse links when said switch part is turned, and terminals for the plug connected respectively with said contact and with the band of said.

fuse element.

6. A fuse plug com rising a tubular body, a tubular switch mem er telescoping in said body to be rotatable therein, means closing the ends of said switch member for confining a large space within said switch member, fuse links supported on the inner side of said body, a contact carried by said switch member and projecting therefrom for selective engagement with the fuse links when said switch member is turned, a metallic rod extending axially through said space in the switch member and connected with said contact, and a screw shell on said body having electrical connection with said links, said inner terminal member being of comparatively large mass and surface whereby to serve as a cooling agent for the disruption products and gases, and a plurality of restricted relief paths from said chamber to the exterior, said paths bein independent of any passageways through w ich said fuse links extend.

7. A fuse plug of the class described comprising a tubular body having a head, a

switch part fitting'within said body and'seate ing at its outer end in said head and having a neck projecting beyond said head whereby it may be turned in said body, fuse links supported on the inner wall ofsaid body lto be confined between said body and switch part, the inner end of said switch 'part being open to form a large chamber and said part having a slot for selectively exposing said fuse links vto the chamber when said part is rotated, a contact on said switch part projecting through said slot for engagement with a selected fuse link, a cap member closing the inner ends of said body and said switch parts, a'comparatively heavy' metal terminal member extending axially through said chamber and having engagement with said' contact, and a screw shell surrounding said body and having electrical connection with said fuse links.

8.-A fuse plug comprising a tubular body part having a head, a tubular switch part having a head seating in the body part head Iand extending outside thereof to be turned `relative to thebody part,'fuse`links applied to .the outer side of said body part and deiiected longitudinally around said part to extend` inwardly along the inner side thereof between the body part and switch part. a capv member engaging the inner ends of said parts and forming with said parts an insulating enclosure for said fuse links, said switch member providing a large chamber between its head and said end closure member, said part.

9. A fuse plug comprising a tubular body part, a tubular switch part rotatable within said body part, sets of outer and inner channels extending longitudinally in the walls oi' said body part, fuse links folded around the end of said body part to engage the outer and inner channels thereof with the inner ends of said links interposed between sai-dV body part and switch part, contact means extending from .said switch part for selective engagement with the fuse links when said switch part is turned, and terminals for the plugconnected respectively with said contact and' with the ends of said fuse links.

10. A fuse plug comprising outer and inner relatively rotatable members, fuse links folded around the end of the outer member to extend along the outside thereof an-d with their inner ends between said members, contact means movable with said inner member for selective engagement with said links during relative rotation of said members, and terminals for the plug connected respectively with said contact means and with the outer ends of said links.

11. A fuse plug comprising a tubular body part, a tubular switch part rotatable within said body part, interengaging heads for said parts, notches in the lower edge of said body part, fuse links folded around said edge to engage in said notches and to extend along the outerl side of said body part and with their inner ends extending between said body part and switch part, contact means movable with said switch part and adapted for selective engagement with the inner ends of said links, a cap engaging the lower edge of said body part and having projections for engaging in said notches whereby to lock the cap to the body part againstrotation thereon, an inner 'contact member extending from said cap into electrical engagement with said contact means, and an outer terminal member surrounding the body part in electrical enparts, fuse links folded around the lower edge of said body part with their outer ends extending along the outer side of said body part and their inner ends extending between ysaid body part and switch part, contact .means movable with said switch part for and into electrical engagement with said contact means, said fuse links having reduced sections within said chamber at the lower end thereof, and an outer terminal member mounted on said body part into electrical engagement with the outer ends of said fuse links and engaging said 'cap to hold it in place.

In testimony whereof I have hereunto subscribed my -mme at Chicago, Cook County,

Illinois.

HENRY RUSKIN.

said body part, said parts having interengaging heads, fuse links folded around the lower edge of saidbody part with their outer ends extendingalong the outside of said body partW and withv their inner ends extending between said body part and switch part, contact means on said switch part for selective engagement with said'fuselinks when said switch part is turned, a cap for engaging the lower ends of said body andl switch parts, an inner terminal member extending from said cap into electrical engagement with said contact means, and an outer terminal member in the v form of a screw'shell having threaded engagement with said body part, said shell beingin electrical engagement with said fuse .links and ihaving a flange engaging said cap to hold it in place.

14. A fuse plug comprising a body part and a switch part rotatable therein, said body part having a head with an inwardly extending ange, said switch provided Awith -a shoulder for engaging said ange and having a neck extending beyond said ange whereby said switch part may be rotated, fuse links supported on the inner side of said bodv part and extending to the outside thereof, a contact means on said switch part for selectively engaging said fuse links when said switch part is rotated, an inner terminal member for said plug having elec- .trical engagement with said contact means,

andl ad outer terninl memlbermounted (liln sai v part an e ectrica ly engaging t e outer ends of said fuse links.-

15. A fuse plug comprising a body part, a bular switch part rotatalle lwithin said body part, said parts having interengaging heads, fuse links arranged against the inner wall of said body part with their ends extending to the exterior of the body part, a cap engllging` the lower edges of said body and switch parts, said switch lpart enclosing' a chamber extending from its head to said cap, a contact means supported in the head of sald switch part for selective engagement with said fuse links when said switch part is turned, an linner terminal for the plug extending from said cap through said chamber part having a head 

